erp5_web_renderjs_ui: appcache document may not exist

bt5/erp5_web_renderjs_ui/SkinTemplateItem/portal_skins/erp5_web_renderjs/Base_getListFileFromAppcache.py

 appcache_reference = context.getLayoutProperty("configuration_manifest_url", default="gadget_erp5.appcache")
 
-text_content = context.getPortalObject().portal_catalog.getResultValue(
+web_manifest = context.getPortalObject().portal_catalog.getResultValue(
   portal_type='Web Manifest',
-  reference=appcache_reference).getTextContent()
+  reference=appcache_reference)
+
+if web_manifest is None:
+  text_content = ''
+else:
+  text_content = web_manifest.getTextContent()
 
 translation_data_url_list = []
 url_list = []

bt5/erp5_web_renderjs_ui/SkinTemplateItem/portal_skins/erp5_web_renderjs/WebSite_checkCacheModificationDateConsistency.py

@@ -7,8 +7,10 @@ error_list = []
 if appcache_reference:
   url_list = context.Base_getListFileFromAppcache()
   # Check that the manifest is newer than all cached resources.
-  appcache_manifest = getDocumentValue(appcache_reference).getObject()
-  appcache_manifest_modification_date = appcache_manifest.getModificationDate()
+  appcache_manifest = getDocumentValue(appcache_reference)
+  if appcache_manifest is not None:
+    appcache_manifest = appcache_manifest.getObject()
+    appcache_manifest_modification_date = appcache_manifest.getModificationDate()
   for url in url_list:
     if url:
       referenced_document = getDocumentValue(url)